As a liquid crystal display and a television set grow constantly in size, the size of an optical film applied in a liquid crystal backlight module increases as well. The optical film will expand because of heating at an edge close to the heat source. Since an optical film is less thermally conductive, the optical film will be warped at the edge close to the heat source due to inhomogeneous heating thereto. When the edge of the optical film is warped from local expansion under heating, there will be side incidence light to enter into the optical film from one side thereof, resulting in the formation of dark shadows in wave shape at the entrance side of the optical film for the side incidence light, and thus in a poor display effect of the liquid crystal display module.
Therefore, in order to improve the display effect of the liquid crystal display model, it is necessary to control the warps at an edge of the optical film due to expansion under heating.